1. Field of the Invention
The present invention relates to an information provision method, an information provision device, and a computer-readable recording medium in which the information provision program is recorded. In particular, the information provision method, the computer-readable recording medium recording the information provision program, and the information provision device are arranged for providing information to one or more mobile terminals in a coverage zone.
2. Description of the Related Art
Conventionally, when a system for a large-scale information provision service is constructed, loads are balanced in order to secure scalability of the system, where the scalability is a degree of adaptability for qualitative and quantitative changes in requests for processing. The load balancing is broadly divided into the zone-based load balancing and the content-based load balancing. In the zone-based load balancing, servers having identical content are assigned on a zone-by-zone basis, for example, on a prefecture-by-prefecture basis, i.e., servers which serve users are assigned according to the positions at which the users establish connections. In the content-based load balancing, servers are assigned on a content-by-content basis, i.e., servers which serve users are assigned according to the content which the users request.
In the case where a predetermined server is assigned for terminals in a predetermined zone according to the zone-based load balancing, errors in detection of the locations of the terminals may create a possibility that a terminal which is actually located inside the zone is determined to be located outside the zone when the location of the terminal is near a boundary of the zone. Therefore, a technique for flexibly determining whether a terminal is located inside or outside a zone is disclosed. For example, in the technique disclosed in Japanese Unexamined Patent Publication No. 2003-27529 (hereinafter referred to as JPP 2003-27529), a hysteresis zone is defined between an operation zone and a nonoperation zone in remote control of a construction machine.
One of services using a load-balancing system is the service for providing to each user shop-information content appropriate for the location of the users' terminal. In many cases where such service is provided, the area over which information is delivered is large, and the number of content items is great. Therefore, in such cases, load balancing is necessary. In the services in which content corresponding to the location of each of users' terminals is provided, it is possible to secure scalability by combining the zone-based load balancing and the content-based load balancing.
When a server assigned to each zone manages content items related to localities in the zone and users' terminals in the zone, it is possible to combine the zone-based load balancing and the content-based load balancing. However, when a user's terminal moves from a first zone covered by a first server to a second zone covered by a second server, operations for the second server inheriting information on the user's terminal from the first server are automatically performed between the first and second servers. Thus, the second server takes charge of the user's terminal.
Nevertheless, according to the above method, the operations for transferring user information on the user's terminal from the first server assigned to the first zone to the second server assigned to the second zone are necessary when the user's terminal moves from the first zone to the second zone. At this time, if processing for data storage into or data acquisition from a database or other similar processing occurs, the calculation cost becomes particularly high. In particular, when the user's terminal continuously moves around a boundary, zone changes frequently occur, so that the loads imposed on the servers become very heavy.
According to the technique disclosed in JPP 2003-27529, when the construction machine moves from the nonoperation zone into the hysteresis zone, it is determined that the construction machine directly enters the operation zone. Therefore, when the construction machine moves around the boundary between the hysteresis zone and the nonoperation zone, the determination whether the construction machine is in the operation zone or in the nonoperation zone successively changes. That is, the technique disclosed in JPP 2003-27529 cannot solve the aforementioned problem.